The usnic acid derivative peziculone targets cell walls of Gram-positive bacteria revealed by high-throughput CRISPRi-seq analysis

New Fe3O4-Based Coatings with Enhanced Anti-Biofilm Activity for Medical Devices

With the increasing use of invasive, interventional, indwelling, and implanted medical devices, healthcare-associated infections caused by pathogenic biofilms have become a major cause of morbidity and mortality. Herein, we present the fabrication, characterization, and in vitro evaluation of biocompatibility and anti-biofilm properties of new coatings based on Fe3O4 nanoparticles (NPs) loaded with usnic acid (UA) and ceftriaxone (CEF). Sodium lauryl sulfate (SLS) was employed as a stabilizer and modulator of the polarity, dispersibility, shape, and anti-biofilm properties of the magnetite nanoparticles. The resulting Fe3O4 functionalized NPs, namely Fe3O4@SLS, Fe3O4@SLS/UA, and Fe3O4@SLS/CEF, respectively, were prepared by co-precipitation method and fully characterized by XRD, TEM, SAED, SEM, FTIR, and TGA. They were further used to produce nanostructured coatings by matrix-assisted pulsed laser evaporation (MAPLE) technique. The biocompatibility of the coatings was assessed by measuring the cell viability, lactate dehydrogenase release, and nitric oxide level in the culture medium and by evaluating the actin cytoskeleton morphology of murine pre-osteoblasts. All prepared nanostructured coatings exhibited good biocompatibility. Biofilm growth inhibition ability was tested at 24 h and 48 h against Staphylococcus aureus and Pseudomonas aeruginosa as representative models for Gram-positive and Gram-negative bacteria. The coatings demonstrated good biocompatibility, promoting osteoblast adhesion, migration, and growth without significant impact on cell viability or morphology, highlighting their potential for developing safe and effective antibacterial surfaces.

Azalomycin F4a targets peptidoglycan synthesis of Gram-positive bacteria revealed by high-throughput CRISPRi-seq analysis

Azalomycin F4a is a promising 36-membered polyhydroxy macrolide that shows antibacterial activity against drug-resistant Gram-positive bacteria, but its exact working mechanism remains to be elusive. Here, we isolated the azalomycin F4a product from a Streptomyces solisilvae and demonstrated its antibacterial activity against Gram-positive pathogens including Streptococcus pneumoniae, Staphylococcus aureus and methicillin-resistant Staphylococcus aureus (MRSA). We further showed that combination of azalomycin F4a with methicillin has an additive antimicrobial effect on MRSA, where the minimal inhibitory concentrations (MIC) of methicillin to MRSA was decreased by 1000-fold in the presence of sublethal concentration of azalomycin F4a. A CRISPRi-seq based whole genome screen was employed to identify the potential targets of azalomycin F4a, which revealed that peptidoglycan synthesis (PGS) was inhibited by azalomycin F4a. Furthermore, azalomycin F4a treatment could significantly impair S. aureus biofilm formation. Our research highlights that cell wall synthesis is an additional target for novel classes of macrolide besides ribosome.